Scummymummy, my favourite comment was: Oh, they're not twins, they don't even look the same!! I didn't think it was worth the effort to reply.
pop, I can understand your apprehension at the prospect of twins - I remember feeling just the same (complete panic actually!). I already had 3 children, who were 4, 3 and 20 months when my boys were born, and I would reiterate what others have said about accepting help from friends, relatives and any other possible source. I was able to afford a cleaner for 4 hours a week, and also had help from social services (the Crisis Team!) which was organised by my midwife. I also had a student nursery nurse for a few hours a week.
As far as breastfeeding goes, your body should produce enough milk for 2 babies (I think feeding them at the same time helps the supply). Mine were in special care for a few days after they were born, and I had to express milk, and it really boosted my confidence to find that I was producing enough for 3 babies!
One thing which might be worth thinking about is asking to have a look round your special care baby unit, since so many twins have to go there for a few days. Mine were very happy to do that, and it reassured me after they were taken there when they were born, as I knew where they were.
My twins are 5 now, and a real delight. And they still attract attention whenever we go out! Good luck.